💾 Data Updated: Latest version • Last updated: December 09, 2025

8540.99.40.00 - Electron guns; radio frequency (RF) interaction structures for microwave tubes of subheadings 8540.71 through 8540.79, inclusive 🖩

Details

FieldValue
Unit of QuantityNo.
General Rate of Duty (Column 1 - General)Free
Special Rate of Duty (Column 1 - Special)N/A
Column 2 Rate of Duty35%
Quota QuantityN/A
Additional DutiesN/A
About Duty Rates: Rates are divided into Column 1 and Column 2. Column 1 is subdivided into General (normal trade relations rates for all countries not eligible for special programs) and Special (preferential rates for countries with free trade agreements or preference programs). Column 2 rates apply to products from Cuba, North Korea, Belarus, and Russia. When no special rate exists for a classification, General rates apply.

Overview

HTS Code 8540.99.40.00 specifically classifies electron guns and radio frequency (RF) interaction structures designed for use in microwave tubes falling under subheadings 8540.71 through 8540.79. Electron guns are the components responsible for generating and accelerating an electron beam, a fundamental element in the operation of many types of vacuum tubes. RF interaction structures are critical for the efficient transfer of energy between the electron beam and the radio frequency fields within the tube, enabling amplification or oscillation. These parts are integral to the functioning of specialized microwave tubes such as magnetrons, klystrons, and traveling-wave tubes.

This subheading is distinguished from its sibling, 8540.99.80.00 ("Other"), by its specificity. While 8540.99.80.00 encompasses all other parts of thermionic, cold cathode, or photocathode tubes not otherwise specified, 8540.99.40.00 precisely identifies specialized components essential for microwave tube technology. Therefore, any part that is an electron gun or an RF interaction structure for the specified microwave tubes must be classified here, rather than in the more general "Other" category.

As this is a leaf node in the HTS classification, there are no further subcategories. Classification under 8540.99.40.00 is final for eligible electron guns and RF interaction structures for microwave tubes. The key determining factors for classification are the physical nature of the component as either an electron gun or an RF interaction structure, and its intended application within the specified subheadings for microwave tubes.

Frequently Asked Questions

›What is HTS code 8540.99.40.00?
HTS code 8540.99.40.00 covers Electron guns; radio frequency (RF) interaction structures for microwave tubes of subheadings 8540.71 through 8540.79, inclusive under the US Harmonized Tariff Schedule. It falls under Chapter 85: Electrical machinery and equipment and parts thereof; sound recorders and reproducers, television image and sound recorders and reproducers, and parts and accessories of such articles.
›What products are classified under 8540.99.40.00?
This classification covers Electron guns; radio frequency (RF) interaction structures for microwave tubes of subheadings 8540.71 through 8540.79, inclusive. It is a subcategory of Other: (8540.99).
›What is the import duty rate for 8540.99.40.00?
The general rate of duty for HTS 8540.99.40.00 is Free. The Column 2 rate is 35%.
›What unit of quantity is used for 8540.99.40.00?
Imports under HTS 8540.99.40.00 are measured in No..

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